RF Sputtering Counter Electrode Cavities
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Solution Overview
Problem
In RF sputtering, the larger counter electrode is often undesirably sputtered, especially when its plasma potential exceeds the sputtering threshold, leading to deposition of unwanted materials on the substrate, and existing solutions like magnetic fields complicate the design or are impractical for large-area applications.
Innovation Solution
A RF sputtering arrangement with a counter electrode featuring cavities that increase its surface area, allowing plasma formation within these cavities, thereby reducing the likelihood of sputtering from the counter electrode, and incorporating a corrugated form with additional electrically conductive members that define these cavities, which can be integrated into the vacuum chamber's walls and base for enhanced surface area without obstructing the deposition path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the counter electrode area is increased to reduce sputtering from the smaller electrode, then the sputtering effect from the smaller electrode is reduced, but the counter electrode itself becomes more prone to sputtering and the apparatus complexity increases
Solution Approach 1:
The counter electrode is designed with a three-dimensional corrugated structure featuring multiple cavities and protrusions, transforming a two-dimensional surface into a multi-dimensional topology. This increases the effective surface area by a factor of 5-10 times without increasing the horizontal footprint, thereby reducing sputtering from the smaller electrode while avoiding the need for additional magnets or complex mechanisms.
Solution Approach 2:
The counter electrode incorporates curved and corrugated surfaces with multiple cavities and protrusions instead of a flat surface. This curved, multi-faceted geometry increases the effective surface area exposed to plasma, enhancing the counter electrode's ability to suppress sputtering from the smaller electrode while maintaining a compact apparatus design.
2Reliability
If magnets are added to the counter electrode to reduce sputtering, then sputtering from the counter electrode is reduced, but the design and manufacture complexity increases
Solution Approach 1:
The patent replaces the magnetic field-based solution (requiring magnets and complex field control) with a purely geometric solution. The corrugated counter electrode structure with increased surface area achieves sputtering suppression through physical geometry alone, eliminating the need for magnets, power supplies, and complex magnetic field management systems.
Solution Approach 2:
The corrugated counter electrode structure provides a simple, cost-effective alternative to expensive magnetic systems. The geometric design uses basic conductive materials formed into corrugated shapes, avoiding the high cost of magnets, magnetic field control electronics, and associated maintenance requirements.
3Reliability
If the counter electrode area is increased to prevent sputtering, then sputtering from the counter electrode is reduced, but the apparatus size increases which is impractical for large-area applications
Solution Approach 1:
The counter electrode utilizes vertical and multi-dimensional corrugations to increase surface area without expanding the horizontal apparatus footprint. The cavities and protrusions extend in the vertical dimension, allowing the effective electrode area to be 5-10 times larger than the horizontal projection area, making the solution practical for large-area substrate processing.
Solution Approach 2:
The corrugated counter electrode structure nests multiple cavities and protrusions within the horizontal footprint of the apparatus. This nested geometry allows the counter electrode to occupy the same horizontal space while providing vastly increased surface area through vertical and multi-level features, avoiding the need for a larger apparatus.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively reduces the sputtering of the counter electrode material onto the substrate, maintaining deposition uniformity and quality while allowing for larger counter electrode areas without the need for additional magnets, thus simplifying the apparatus and accommodating larger substrates like 30cm diameter wafers.
Implementation Method 1
A RF generator is provided which is configured to apply a RF electric field across the at least one first electrode and the counter electrode so as to ignite a plasma between the first electrode and the counter electrode
Implementation Method 2
ignite a plasma between the first electrode and the counter electrode
Implementation Method 3
The counter electrode comprises at least two cavities in communication with the vacuum chamber. The cavities each have dimensions such that a plasma can be formed in the cavity
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
Apparatus for sputtering comprises a vacuum chamber, at least one first electrode having a first surface arranged in the vacuum chamber, a counter electrode having a surface arranged in the vacuum chamber and a RF generator. The RF generator is configured to apply a RF electric field across the at least one first electrode and the counter electrode so as to ignite a plasma between the first electrode and the counter electrode. The counter electrode comprises at least two cavities in communication with the vacuum chamber, the cavities each have dimensions such that a plasma can be formed in the cavity.